In modern fuel supply systems, water separators are normally used in the associated fuel filter devices to reduce a water fraction in the fuel as much as possible. If the water in the fuel is not separated out, undesirable corrosion, abrasion, material embrittlement and cavitation can result in the assemblies downstream. An elevated water fraction in the fuel supply system likewise promotes the growth of micro-organisms, which can cause slime formation in the fuel filter device and increased corrosion of the filter housing. What are known as coalescers are normally used as water separators, which coalesce the extremely small water fractions to form larger water droplets and separate these out of the fuel-water emulsion using gravity. If necessary for the water separation, what is known as a final separator, consisting of a hydrophobic fabric, can also filter out the water droplets in the fuel-water emulsion. The water separated out in this manner is then collected in separate water collection spaces, from which it is drained periodically or at the latest when the filter element is changed.
DE 10 2010 062 813 A1 discloses a filter device for an internal combustion engine of a motor vehicle, in particular a fuel or lubricant filter, having a filter housing and an annular filter element, which is arranged in the filter housing and through which flow passes in a radial direction from an untreated side to a clean side. A water separator is arranged on the clean side of the filter element and below same, said water separator having a hydrophobic, annular membrane, through which fuel/lubricant can pass radially inwards from the radial outside and which extends in the axial direction of the filter element. This is intended to improve the level of water separation. This is a classical coalescer.
The disadvantages of the water separators known from the prior art are that they only have a limited service life, performance sometimes decreases considerably towards the end of the service life, and therefore they should periodically be changed, for example.